Panasonic Intermittent Use

[lemmy]

My e-bike use will probably settle to using my normal bike for local trips and my Agattu for longer ones of 15-40 miles once, sometimes twice per week.

Will this intermittent use impinge on battery life or charging capacity in any noticeable way - shorten or lengthen it from the 3 or so years I would hope for?

If I were to undertake a series of trips of 2-4 miles, would it be best to charge after each one or leave it for several trips until the charge is low?

 

[Barry Heaven]

Good question. My understanding is that to maximise the life of lithium batteries it is best to recharge after every ride, even after short ones. I do wonder through whether it is worth it for very short rides.

 

[flecc]

Don't charge for two to four miles use, since charging does give some stress to the battery cells, so there's a balance between the avoidance of full discharge and too frequent charging. Basically aim to charge when a third or more of capacity is used, avoiding charging at less than a quarter used.

The intermittent use of the type you describe won't do any harm.
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[Barry Heaven]

Thanks Flecc. So for the Panasonic system try to avoid charging when there are still at least 4 lights showing on the battery gauge?

 

[lemmy]

Thanks for that.

 

[flecc]

Thanks Flecc. So for the Panasonic system try to avoid charging when there are still at least 4 lights showing on the battery gauge?

Yes, that's a good indicator of when to avoid charging, unless it's absolutely necessary for a following long journey which needs all the capacity.
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[lemmy]

Given that the battery in question is rated at circa 500 recharge cycles, would it make any difference if that comprised 50 per annum over 10 years or 500 over one year?

Or is a ten year life out of the question because of chemical deterioration? Do 500 charges to full capacity from half charge take the life of the battery to likely exhaustion or would it take 1000 half charges?

So many interesting questions that probably have no definitive answers.

An interesting aside. My brother who has an electronic design business, when a kid, used to fool around reconstituting nicad batteries. He said that if you took apart one that had given up the ghost, you saw an effect he called whiskering. If you applied a large current to such a cell, it would either explode or would be reactivated, albeit with a much shorter life than originally. The explosion was much more fun than a reusable battery.

 

[flecc]

Given that the battery in question is rated at circa 500 recharge cycles, would it make any difference if that comprised 50 per annum over 10 years or 500 over one year?

Or is a ten year life out of the question because of chemical deterioration? Do 500 charges to full capacity from half charge take the life of the battery to likely exhaustion or would it take 1000 half charges?

So many interesting questions that probably have no definitive answers.

There are some definitive answers with lithium batteries, delending on usage conditions. With the exception of lithium iron phosphate, if used under tyical e-bike conditions they chemically deteriorate whether used or not, generally limiting their life to around two to three years.

There are variations:

1000 half charges is only roughly pro rata to 500 full charges since there is some loss of life due to cell stress as full charge is approached. Obviously that's twice the stress for the 1000 part charges.

A battery used only between 20% and 80% of charge, never being completely emptied once conditioned and never being taken to full cell charge can last for much longer. When only one seventh of the charge is gently and slowly used between those points each day, the battery can last for up to ten years of daily charging. That's how those in satellites are run, but not practical for e-biking of course.

The Panasonic battery has a sleepmode which disconnects the internal BMS electronics typically after a couple of weeks of not being used. That stops the small current drain of the circuit which reduces the chemical usage of the battery, making it last a bit longer.

Lithium iron phosphate ( LiFePO4) can last from double the normal lithium life of other types up to about ten years in theory, but that has yet to be proved in practical circumstances.
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